Ultraviolet irradiation (UVB) interrupts calcium cell signaling in lens epithelial cells

A preliminary study was undertaken to establish whether low-dose UV irradia tion (UVB) affects calcium cell signaling in rabbit lens epithelia. In a su spension of lens epithelial cells (line NN1003A), changes in intracellular Ca2+ were measured by Fura-2 fluorescence in response to exogenously added ATP, The cellular response to ATP, referred to as the calcium signal, is ch aracterized by a brief increase and subsequent decrease in cytosolic Ca2+ l evels. Ultraviolet B irradiation (1.8-9 mJ/cm(2)) was found to reduce the m agnitude of the Ca2+ signal in a dose-dependent manner. A 5 min UVB exposur e (9 mJ/cm(2)) completely altered the biphasic nature of the calcium signal , causing only an immediate and steady rise in cytosol Ca2+ levels. Lower f luences of UVB irradiation (2 min exposure times or 3.6 mJ/cm(2)) induced a 50% reduction in the calcium signal. When irradiated cells were returned t o culture for 3 h after irradiation, calcium signals induced by ATP were no rmal. In view of the photooxidative nature of UVB irradiation, the oxidativ e state of cells was assessed by measuring glutathione (GSH) levels. Ultrav iolet B irradiation caused a rapid 20% decline in GSH levels that returned to near-control values after a 3 h postirradiation incubation. The results of this study indicate that fluences lower than previously found to be cata ractogenic can perturb calcium cell signaling in cultured lens epithelial c ells.